users_controller.rb

class UsersController < ApplicationController #for formalities, you know...

	#for user login we would typically use a sessions controller, but for the sake of the assignment we'll call that `#new_user_session` within this controller

	def new
		@user = User.new
	end

	#user registration with no auth
	def create
		@user = User.new(user_params)
		if @user.save
			# signin user and redirect
			flash[:success] = 'SUCCESS!'
			redirect_to root_path # assuming views
		else
			# Errors handled by model validation
			render :new
		end
	end

	#SessionsController
	def new_user_session
		#assuming lots, but this will basically grab from MySQL db if exists
		user = User.find_by(email: params[:email])

		if user #and other auth here conditionally
			sign_in user #function will be handled by sessions controller - example in comments following
			redirect_to root_path #depending on starting page
		else
			flash[:error] = 'Invalid credentials!'
			redirect_to new_user_session
		end
	end

  # Example of sessions sign_in(user)
	# def sign_in(user)
	# 	cookies_here
	# 	remember_tokens
	# 	update_actions_for_valid_sessions
	# 	reset_current_user_as_current_user
	# end

	private

	#strong parameters ie, whitelisted params
	def user_params
		params.require(:user).permit(:email, :password, :type)
	end
end